Mongolian Gerbils Can Utilize Provitamin-A Carotenoids in Deep-Fried Carrot Chips1

Nutrient Metabolism

Mongolian Gerbils Can Utilize Provitamin-A Carotenoids
in Deep-Fried Carrot Chips1
Ahmad Sulaeman,2 David W. Giraud, M. Michelle Naslund and Judy A. Driskell3
Department of Nutritional Science and Dietetics, University of Nebraska, Lincoln, NE 68583-0806

KEY WORDS:

●

carrot chips

●

carotenoids

●

vitamin A

Vitamin A is important for vision, gene expression, reproduction, embryonic development, growth, and immune function (1). Humans need ⬍1 mg of vitamin A daily to maintain
health, yet it was estimated that 3 to 10 million children,
mostly in developing countries, become xerophthalmic and
250,000 to 500,000 go blind annually (2). An additional 250
million children under 5 y of age were estimated to be subclinically vitamin A-deficient and at risk of severe morbidity
and premature death (3).
Due to the enormous cost of vitamin A deficiency to
society, vitamin A intervention is of importance. Vitamin A
intervention approaches are commonly grouped into two main
control strategies: direct increase in vitamin A intake through
dietary modification with natural or fortified foods and supplements and indirect public health measures to control disease
frequency (4). For improving vitamin A status, food-based
approaches could be most effective where there is widespread
availability, variability, adequacy, and acceptability of vitamin
A-containing foods among targeted populations (3). In addition, food-based approaches deserve attention because they are

●

gerbil

more likely to be sustainable in the long term and will increase
the intake of other nutrients simultaneously (5). Such foods
are vegetables and fruits that have high provitamin-A carotenoid concentrations, especially ␤-carotene.
Deep-fried carrot chips that are high in provitamin-A carotenoids were developed in our laboratory as an alternative
product for intervention programs to overcome vitamin A
deficiency (6). Carrot chips contain fat, which is important
and a key factor in carotene absorption (7,8). Underwood (4)
reported that vegetable food-based interventions in vitamin
A-deficient areas can successfully improve vitamin A status,
particularly when dietary fat levels are also increased sufficiently. Carrot chips have a pleasant taste and an appealing
appearance; laboratory sensory evaluation and consumer studies indicated that this product was acceptable to both American and Southeast Asian consumers (unpublished data). The
retention of provitamin-A carotenoids during storage was
above 80%, which is important for optimal usage of this
product (9).
Using the conversion factors given by the National Research Council in 1989 (10), the deep-fried carrot chips developed in our laboratory had vitamin A activities of 7322–
8532 ␮g retinol equivalents (RE)4/100 g chips (11). Using the
new conversion factors (1), this product had vitamin A activities of 3661– 4266 ␮g retinol activity equivalents (RAE) per
100 g chips, an amount high enough to satisfy the human adult
daily need for vitamin A. However, to accurately measure the
biological activity of provitamin-A carotenoids in the carrot

1
Supported in part by the Nebraska Agricultural Research Division and
Research Report 13484.
2
Current address: Department of Community Nutrition and Family Resources, Bogor Agricultural University, IPB Darmaga Campus, Bogor 16680,
Indonesia.
3
To whom correspondence should be addressed. E-mail: jdriskell@unl.edu
4
Abbreviations used: BC, ␤-carotene-containing diet; CC, carrot chip-containing diet; RAE, retinol activity equivalents; RE, retinol equivalents; ⫹VA, vitamin
A-containing diet; ⫺VA, diet containing no vitamin A/provitamin-A carotenes.

0022-3166/02 $3.00 © 2002 American Society for Nutritional Sciences.
Manuscript received 5 September 2001. Initial review completed 16 October 2001. Revision accepted 15 November 2001.
211

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ABSTRACT Deep-fried carrot chips, containing provitamin-A carotenes, were developed as an alternative mode

of dietary intervention to combat vitamin A deficiency. The biological use of carotenoids in this product as vitamin
A precursors was evaluated in Mongolian gerbils. Male 4-wk-old gerbils were fed a diet containing all essential
nutrients for 1 wk. Then six gerbils were killed, and the remaining gerbils were fed the diet without vitamin A for 6
wk to produce marginal vitamin A deficiency. After depletion, six gerbils were killed and the remainder divided into
four groups of 12 gerbils each and fed vitamin A-containing diet (⫹VA), ␤-carotene-containing diet (BC), carrot
chip-containing diet (CC), or diet containing no vitamin A/provitamin-A carotenes (⫺VA). The first three diets
contained ⬃6 ␮g RE/g. Six gerbils from each group were killed after 2 wk of consuming these diets, and 6 after
4 wk. Final body weight and weekly food consumption did not differ among groups after 2 or 4 wk of repletion. Total
liver vitamin A stores of BC and CC gerbils killed after 4 wk of repletion were not different from those of gerbils killed
before depletion, but those of ⫺VA gerbils were significantly lower (P ⬍ 0.05) and those of ⫹VA gerbils were
significantly higher (P ⬍ 0.05). Plasma retinol levels of gerbils killed after 4 wk of repletion, including the ⫺VA group,
did not differ. Total liver ␣- and ␤-carotenes and 9-cis ␤-carotene contents of the CC group were significantly
higher (P ⬍ 0.05) than in the BC group after 4 wk of repletion. This carrot chip product effectively reversed vitamin
A deficiency in gerbils. J. Nutr. 132: 211–217, 2002.

SULAEMAN ET AL.

212

chips, a biological activity study using animal models was

conducted.
The appropriate animal model should closely mimic the
human uptake, absorption, and metabolism of vitamin A,
␤-carotene, and other carotenoids (12). Recently, the Mongolian gerbil (Meriones unguiculatus) has been suggested as a
possible model for carotenoid metabolism studies (13). Mongolian gerbils can both cleave ␤-carotene and absorb it intact
(14). House et al. (13) demonstrated that male gerbils grow
normally when fed the AIN-93G rodent diet and absorb large
amounts of ␤-carotene. Lee et al. (15) indicated that gerbils
convert ␤-carotene to vitamin A at a ratio similar to that of
humans. Therefore, Lee et al. (15) suggested that the Mongolian gerbil is an appropriate animal model for evaluation of the
conversion of ␤-carotene to vitamin A.
This study was designed to evaluate the biological utilization of carotenoids present in the newly developed deep-fried
carrot chip product and to examine whether this chip product
could be used to improve the vitamin A status of the Mongolian gerbil.
MATERIALS AND METHODS

TABLE 1
Composition of powdered diet fed to gerbils during adaptation, depletion, and repletion periods1
Ingredient

⫹VA diet2

⫺VA diet

BC diet

CC diet

200
3
392.4699
200
58
42
50
50
0.0004
0.03
0.066
3.5

0.002
0.11
0.05
0.099
0.022
0.022
0.022
0.0044
0.2423
—
0.36
—

200
3
367.8247
200
58
—
43

50
0.0004
0.03
0.066
3.5
0.002
0.11
0.05
0.099
0.022
0.022
0.022
0.0044
0.2423
—
—
74

g/kg
Casein

dl-Methionine
Dextrose, monohydrate
Sucrose
Safflower oil
Partially hydrogenated soybean oil
Cellulose
Mineral mix (Hegstead IV)3
Biotin
Vitamin B-12 (0.1% in mannitol)
Calcium pantothenate
Choline dihydrogen citrate
Folic acid
Inositol
Menadione
Niacin
Pyridoxine hydrochloride
Riboflavin
Thiamin hydrochloride
Vitamin D-3, cholecalciferol (500,000 IU/g)
dl-␣-tocopherul acetate (500 IU/g)

Vitamin A palmitate (500,000 IU/g)
␤-carotene, beadlet form (10%)
Ground carrot chips

200
3
392.7899
200
58
42
50
50
0.0004
0.03
0.066
3.5
0.002
0.11
0.05
0.099

0.022
0.022
0.022
0.0044
0.2423
0.04
—
—

200
3
392.8299
200
58
42
50
50
0.0004
0.03
0.066
3.5
0.002
0.11
0.05
0.099
0.022
0.022
0.022
0.0044
0.2423
—
—
—

1 Described by Thatcher et al. (17).
2 ⫹VA diet contained vitamin A; ⫺VA diet contained no vitamin A or carotenoids; BC diet contained ␤-carotene, and CC diet contained carrot

chips.
3 The mineral mix (Hegstead IV, Teklad, Madison, WI) supplied the following (g/kg diet): calcium carbonate, 299.7452; potassium phosphate,
dibasic, 322.226; calcium phosphate, dibasic, 74.9363; magnesium sulfate, 101.9134; sodium chloride, 167.3577; ferric citrate, USP (16.7% Fe),
27.4766; potassium iodide, 0.79932; manganese sulfate, 3.78527; zinc chloride, 0.249788; cupric sulfate, 0.299745; and cellulose, 1.210677.

Downloaded from jn.nutrition.org by on June 23, 2007

Deep-fried carrot chips. Deep-fried carrot chips were developed
in our laboratory based on the treatment that resulted in optimal
carotenoid retention and the best sensory acceptability (6,9,11).
Carrot chips were packaged in vacuum-sealed layered film (2.50 mil,
or 0.0625-mm thick, metallized polyester and linear low density
polyethylene) pouches (16.5 cm ⫻ 20.3 cm o.d.; Kapak, Minneapolis,
MN) using a Multivac AG 500/AG900 (Multivac Kansas City, MO)
and stored at ⫺50°C until ready for use in the diet. The carrot chips

were ground and analyzed before use in the diet. The mean composition of the deep-fried carrot chips was as follows: (per 100 g) energy,
2604.3 kJ (622 kcal); moisture, 3.3 g; crude fat, 56.8 g; crude protein,
3.8 g; dietary fiber, 9.8 g; ash, 2.3 g; and vitamin A activity, 4050
RAE.
Animals. After approval by the University’s Laboratory Animal
Care and Use Committee, male 4-wk-old (weanling) Mongolian
gerbils (n ⫽ 72) with average weights of 28 –32 g were obtained from
Harlan Sprague-Dawley (Madison, WI). Upon arrival, the gerbils
were individually housed in suspended cages. The gerbils had free
access to food and distilled water, and room lighting was on a diurnal
cycle (12-h light:12-h dark).
Diets. The powdered diet described by Thatcher et al. (16),
purchased from Harlan Teklad (Madison, WI), was used (Table 1).
The composition of this diet is consistent with the recommendations
of the National Research Council (17) except for vitamin A. The
above diet contained vitamin A (20.9 nmol/g diet as retinyl palmitate
in beadlet form) (15). This diet was modified to contain either no
vitamin A (including no provitamin-A carotenoids), ␤-carotene
(65.1 nmol/g diet in beadlet form) (15), or ground carrot chips
(amount of carrot chips equivalent to an estimated vitamin A activity
of 20.9 nmol/g diet). All diets, except the diet lacking vitamin A, had
equivalent estimated vitamin A activities (6 ␮g RE/g diet) using the
conversion factors given by the National Research Council (10).
These four diets were adjusted to be equal in fat content. The diets
were stored at 5°C until used. Before feeding and after several months
of storage, the diets were analyzed for retinoid and carotenoid content (18).
Experimental design. The gerbils were fed the powdered diet
containing vitamin A (20.9 nmol/g diet) for 1 wk. After acclimation
for 1 wk, six randomly selected gerbils were killed and the remainder
fed the diet without vitamin A for 4 or for 6 wk to produce marginal
vitamin A status. After this depletion period, six randomly selected

CAROTENOIDS IN CARROT CHIPS AS PROVITAMIN-A

FIGURE 1 Experimental design of gerbil-feeding trial with ␤-carotene-containing (BC), carrot chip-containing (CC), vitamin A-containing (⫹VA), and containing no vitamin A/provitamin-A carotenes (⫺VA)
diets.

TABLE 2
Final body weight and food consumption of gerbils at
baseline, after depletion, and after repletion with different
diets (BC, CC, ⫹VA, and ⫺VA diets) for 2 or 4 wk1,2
Experimental diet

Final weekly food
consumption

Final body weight
g

Baseline
Depleted 4 wk
Depleted 6 wk
BC repleted 2 wk
BC repleted 4 wk
CC repleted 2 wk
CC repleted 4 wk
⫹VA repleted 2 wk
⫹VA repleted 4 wk
⫺VA 2 wk
⫺VA 4 wk

42.3 ⫾ 2.4c
51.8 ⫾ 5.7b
56.4 ⫾ 4.5b
60.7 ⫾ 4.9ab
60.5 ⫾ 7.6ab
62.1 ⫾ 7.5ab
60.5 ⫾ 5.0ab
60.1 ⫾ 3.7ab
64.7 ⫾ 4.8a
62.8 ⫾ 3.9ab
61.2 ⫾ 4.3ab

38.2 ⫾ 1.7
42.3 ⫾ 3.0
38.4 ⫾ 4.6
37.7 ⫾ 4.8
40.8 ⫾ 2.5
38.0 ⫾ 5.0
36.1 ⫾ 4.0
38.0 ⫾ 2.8
40.0 ⫾ 2.8
37.2 ⫾ 3.3
40.0 ⫾ 3.8

1 Values are means ⫾ SD, n ⫽ 6. Values within a column with the
same superscripts are not different, P ⱖ 0.05.
2 Gerbils on baseline fed vitamin A-containing diet; gerbils on depletion fed vitamin A-deficient diet; gerbils on repletion fed either BC,
␤-carotene-containing diet; CC, carrot chip-containing diet; or ⫹VA,
vitamin A-containing diet. These three diets had vitamin A activity ⬃6
␮g RE/g diet. The ⫺VA groups continued on depleted diet for an
additional 2 and 4 wk period.

RESULTS
Food consumption and growth performance. The growth
performance and weekly diet consumption of gerbils during
adaptation, depletion, and repletion periods are presented
in Table 2. There were no significant effects (P ⱖ 0.05) of
diet on weekly food intakes and body weights of the gerbils.
There were no significant differences (P ⱖ 0.05) in final
body weight and weekly food consumption among the four
groups.
Liver stores of vitamin A. The gerbils were marginally
deficient in vitamin A (15) after consuming the vitamin
A-deficient diet for 6 wk as the liver retinol decreased from
0.51 ␮mol/g (0.94 ␮mol/liver) to 0.20 ␮mol/g (0.60 ␮mol/
liver; Table 3). Liver vitamin A stores of the BC and CC
groups returned to predepletion (or baseline) levels after 4 wk
of repletion, and after 2 wk of repletion for ⫹VA gerbils. After
being repleted for 4 wk, the liver vitamin A stores were not
significantly different from the baseline for BC and CC groups,
were higher for the ⫹VA groups, and were lower in the ⫺VA
group (P ⬍ 0.05).
Plasma retinol. The mean plasma retinol concentrations
of the BC, CC, ⫹VA, and ⫺VA groups after 4 wk of repletion
were: 1.47, 1.33, 1.40, and 1.40 ␮mol/L (42.17, 38.06, 40.16,
and 40.12 ␮g/dL), respectively (Table 3), which, except for
the BC group, were not different (P ⱖ 0.05) from baseline.
Plasma retinol did not differ among gerbils in the four diet
groups after 4 wk repletion. Serum levels ⬍ 0.7 ␮mol/L (20
␮g/dL) are considered to be indicative of subclinical vitamin
A inadequacy (4) or marginal deficiency in humans. There was
no significant correlation between plasma retinol concentrations and liver stores of retinol.
Plasma and liver carotenes. ␣-Carotene, ␤-carotene, and
9-cis ␤-carotene were not detectable in plasma of gerbils in all
diet groups nor were ␣-carotene, ␤-carotene, and 9-cis ␤-carotene in livers of gerbils fed the ⫹VA and ⫺VA diets. Livers

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gerbils were killed, and the remaining gerbils were randomly divided
into four groups of 12 gerbils each and fed either: vitamin Acontaining diet (⫹VA group), ␤-carotene-containing diet (BC
group), carrot chip-containing diet (CC group; these three diets
contained similar vitamin A activity ⬃6 ␮g RE/g diet), or a diet
containing no vitamin A or provitamin-A carotenoids (⫺VA group).
Six gerbils from each of the groups were killed after 2 wk of consuming these diets, and the other six after 4 wk. This experimental design
is summarized in Figure 1. All gerbils were weighed and food consumption determined weekly.
Tissue sampling and analyses. At the time of killing, blood
samples were collected using heparinized syringes via cardiac puncture in gerbils anesthetized with a mixture of ketamine hydrochloride
(Vetlar; Parke-Davis, Morris Plains, NJ) and xylazine (Rompun;
Miles Laboratory, Shawnee, KS; 90:10, v/v), delivered by intramuscular injection (0.1 mL/100 g body), as recommended by Lee et al.
(15). Blood samples were kept in ice, centrifuged at 3000 ⫻ g at 5°C
for 10 min, and plasma frozen at ⫺50°C for future analyses. Livers
were removed, weighed, placed immediately on dry ice, and stored for
future analyses at ⫺50°C.
The method of Nierenberg and Nann (19) was utilized for plasma
carotenoid and retinoid analyses. The liver was extracted according
to Lederman et al. (12) with the following modification: the residue
obtained following hexane extraction and evaporation was resuspended with 100 ␮L tetrahydrofuran, then 50 ␮L mobile phase was
added, and the mixture was sonicated. The volume was brought to
500 ␮L by adding 350 ␮L mobile phase, and 20 ␮L was injected into
the HPLC system for carotenoid (450 nm) and retinoid (325 nm)
analyses.
The HPLC system consisted of the following Waters Associates
(Milford, MA) equipment: 600E solvent delivery system, Pheodyne,
484 UV detector, and 74SB integrator. The separation was carried
out using a reversed phase Microsorb-MV (5-␮m, 250 ⫻ 4.6 mm) C18
column (Rainin, Woburn, MA) that was protected with a guard
column of C18 material (3 cm length ⫻ 4.6 mm i.d.) packed with
spheri-5-C18 (5-␮m particle size). The mixture of acetonitrile:tetrahydrofuran:methanol:1% ammonium acetate (65:25:6:4) was used as
the mobile phase under isocratic conditions (19,20). Minimum detectable levels (per injection) for ␣-carotene, ␤-carotene, and retinol
were 0.075, 0.093, and 0.175 pmol, respectively. The percentage of
recoveries of spiked standards of carotenes and retinol were between
92 and 101, and the CV were ⬍6%.
Plasma triglyceride, total cholesterol, and HDL cholesterol were
analyzed according to Carr et al. (21). LDL ⫹ VLDL cholesterol was
calculated by subtracting the HDL cholesterol from total cholesterol.
Statistical analyses. Data were analyzed by using the General
Linear Model procedure of SAS, Version 6 (SAS Institute Inc., Cary,
NC). Duncan’s multiple range tests were performed for multiple
comparisons to determine differences among groups. Differences were
considered significant at P ⬍ 0.05. Values were expressed as group
means ⫾ SD.

213

SULAEMAN ET AL.

214

TABLE 3
Liver retinol stores and plasma retinol concentrations of
gerbils at baseline, after depletion, and after repletion with
different diets (BC, CC, ⫹VA, and ⫺VA diets) for 2 or 4 wk1,2
Experimental diet

Baseline
Depleted 4 wk
Depleted 6 wk
BC repleted 2 wk
BC repleted 4 wk
CC repleted 2 wk
CC repleted 4 wk
⫹VA repleted 2 wk
⫹VA repleted 4 wk
⫺VA 2 wk
⫺VA 4 wk

Liver retinol stores

Plasma retinol

␮mol/liver

␮mol/L

0.94 ⫾ 0.07bc
0.91 ⫾ 0.17bc
0.60 ⫾ 0.11dc
0.65 ⫾ 0.10de
0.90 ⫾ 0.26bc
0.77 ⫾ 0.13cd
0.95 ⫾ 0.25bc
1.04 ⫾ 0.18b
1.64 ⫾ 0.31a
0.53 ⫾ 0.08e
0.44 ⫾ 0.14e

1.18 ⫾ 0.07c
1.46 ⫾ 0.21ab
1.45 ⫾ 0.09ab
1.57 ⫾ 0.28a
1.47 ⫾ 0.23ab
1.31 ⫾ 0.17bc
1.33 ⫾ 0.08bc
1.32 ⫾ 0.09bc
1.40 ⫾ 0.14abc
1.42 ⫾ 0.09ab
1.40 ⫾ 0.24abc

of gerbils fed the CC diet contained ␣- and ␤-carotenes and
9-cis ␤-carotene, and those fed the BC diet contained only
␤-carotene and 9-cis ␤-carotene (Table 4). Liver ␤-carotene
and 9-cis ␤-carotene stores of the CC group were significantly
higher (P ⬍ 0.05) than those of the BC group after 4 wk of
repletion, but not after 2 wk (Table 4).
Plasma triglyceride and cholesterol. Plasma triglyceride
and HDL cholesterol concentrations did not differ among
groups after 2 wk repletion (Table 5). However, plasma LDL
⫹ VLDL cholesterol and total cholesterol concentrations of
BC-fed gerbils after 2 wk were significantly different (P
⬍ 0.05) from those fed ⫹VA. Plasma triglyceride, LDL ⫹
VLDL cholesterol, HDL cholesterol, and total cholesterol
concentrations did not differ among groups after 4 wk of
repletion. No significant correlations were observed between
carotene concentrations and all the plasma lipid concentrations.
DISCUSSION
In the current study, growth performance was not shown to
be a good indicator for evaluation of carotenoid bioavailability
and bioconversion. Similar findings had previously been reported by other researchers (15,16,22,23). In our study, the
gerbils were only depleted until reaching marginal deficiency,
and no visible signs of deficiency were observed in these
depleted gerbils.
Vitamin A content of the liver is the most commonly used
variable for assessing the vitamin A potency of natural provitamin-A carotenoids (24). Olson (25) reported that in healthy
individuals, ⬃90% of vitamin A in the body is stored in the
liver, and this percentage decreases to 50% or less in severely
deficient individuals. Hepatic vitamin A stores, thus, can be
interpreted to reflect nutrient adequacy to meet total body
needs, barring factors that impede their release into circulation
(1). Liver retinol stores may originate from preformed dietary
retinoids or from provitamin-A carotenes by enzymatic con-

TABLE 4
Liver stores of carotenes of gerbils at baseline, after
depletion, and after repletion with different diets (BC, CC,
⫹VA, and ⫺VA diets) for 2 or 4 wk1,2
Experimental diet

␣-carotene

␤-carotene

9-cis ␤-carotene

nmol/liver
Baseline
nd
nd
Depleted 4 wk
nd
nd
Depleted 6 wk
nd
nd
BC repleted 2 wk
nd
8.47 ⫾ 3.15b
BC repleted 4 wk
nd
14.73 ⫾ 4.62b
CC repleted 2 wk
9.87 ⫾ 2.50b 12.55 ⫾ 3.17b
CC repleted 4 wk
16.50 ⫾ 6.59a 22.39 ⫾ 9.68a
⫹VA repleted 2 wk
nd
nd
⫹VA repleted 4 wk
nd
nd
⫺VA 2 wk
nd
nd
⫺VA 4 wk
nd
nd

nd
nd
nd
2.33 ⫾ 0.61b
3.82 ⫾ 0.50b
2.81 ⫾ 0.80b
5.48 ⫾ 2.16a
nd
nd
nd
nd

1 Values are means ⫾ SD, n ⫽ 6. Values within a column with the
same superscripts are not different, P ⱖ 0.05. nd ⫽ not detectable.
2 Gerbils on baseline fed vitamin A-containing diet; gerbils on depletion fed vitamin A-deficient diet; gerbils on repletion fed either BC,
␤-carotene-containing diet; CC, carrot chip-containing diet; or ⫹VA,
vitamin A-containing diet. These three diets had vitamin A activity ⬃6
␮g RE/g diet. The ⫺VA groups continued on depleted diet for an
additional 2 and 4 wk period.

Downloaded from jn.nutrition.org by on June 23, 2007

1 Values are means ⫾ SD, n ⫽ 6. Values within a column with the
same superscripts are not different, P ⱖ 0.05. nd ⫽ not detectable.
2 Gerbils on baseline fed vitamin A-containing diet; gerbils on depletion fed vitamin A-deficient diet; gerbils on repletion fed either BC,
␤-carotene-containing diet; CC, carrot chip-containing diet; or ⫹VA,
vitamin A-containing diet. These three diets had vitamin A activity ⬃6
␮g RE/g diet. The ⫺VA groups continued on depleted diet for an
additional 2 or 4 wk period.

version (24). Hepatic retinol stores of the gerbils in the CC
group after 4 wk of repletion was more than double that of the
nonrepleted group (⫺VA). Provitamin-A carotenoids present
in deep-fried carrot chips were biologically available in that
vitamin A suboptimacy was reversed by supplementation with
the carrot chip diet containing similar amounts of carotenes as
the ␤-carotene-containing diet. The liver vitamin A stores in
the CC group were significantly higher than in the nonrepleted group (⫺VA), indicating that carotenes in the carrot
chips were absorbed and then converted into vitamin A. Lee
et al. (15), using diets containing the same amounts of vitamin
A or ␤-carotene as in the current study, found that liver
vitamin A levels in gerbils were reversed after 31 d of repletion.
Based on the provitamin-A carotenoid analyses using
HPLC and vitamin A activity calculations using the RAE (1),
a serving of 30 g deep-fried carrot chip product contained
enough vitamin A activity to satisfy the vitamin A requirement of human adults. In this research, the investigators
examined whether the provitamin-A carotenoids of the carrot
chips were biologically available and able to reverse vitamin A
deficiency by monitoring the growth performance and retinoid
and carotenoid levels in liver and plasma of the Mongolian
gerbils. The CC, BC, and ⫹ VA diets had equivalent estimated vitamin A activities as RE, based on the conversion
factors given by the National Research Council (10). However, the liver stores of retinol of CC and BC groups after 4 wk
of repletion were only 55–58% of that of the ⫹VA group.
Hence, the efficiency in which the provitamin-A carotenoids
were converted into retinol in the liver is in agreement with
the new conversion factors using RAE (1), where 1 ␮g RAE is
equal to 12 ␮g ␤-carotene or 24 ␮g ␣-carotene.
Plasma retinol concentration was not a good indicator of
vitamin A deficiency in this study. Lee et al. (15) reported that
serum retinol concentrations of gerbils did not differ among
several dietary groups, including a group fed no vitamin A or

CAROTENOIDS IN CARROT CHIPS AS PROVITAMIN-A

215

TABLE 5
Plasma triglyceride, LDL⫹VLDL-, HDL-, and total cholesterol concentrations of gerbils at baseline, after depletion, and after
repletion with different diets (BC, CC, ⫹VA, and ⫺VA diets) for 2 or 4 wk1,2
Experimental diet

Triglyceride

LDL-⫹VLDL-cholesterol

HDL-cholesterol

Total cholesterol

0.83 ⫾ 0.06c
1.54 ⫾ 0.48b
1.80 ⫾ 0.35ab
2.09 ⫾ 0.27a
1.93 ⫾ 0.27ab
2.02 ⫾ 0.35a
2.14 ⫾ 0.47a
1.88 ⫾ 0.21ab
2.11 ⫾ 0.31a
1.90 ⫾ 0.28ab
1.91 ⫾ 0.19ab

2.47 ⫾ 0.34c
3.08 ⫾ 0.98abc
3.47 ⫾ 0.78ab
3.83 ⫾ 0.45a
2.88 ⫾ 0.42bc
3.24 ⫾ 0.47abc
3.07 ⫾ 0.89abc
2.97 ⫾ 0.28bc
2.84 ⫾ 0.33bc
3.08 ⫾ 0.63abc
2.64 ⫾ 0.25bc

mmol/L
Baseline
Depleted 4 wk
Depleted 6 wk
BC repleted 2 wk
BC repleted 4 wk
CC repleted 2 wk
CC repleted 4 wk
⫹VA repleted 2 wk
⫹VA repleted 4 wk
⫺VA 2 wk
⫺VA 4 wk

0.073 ⫾ 0.032c
0.126 ⫾ 0.061bc
0.172 ⫾ 0.081abc
0.272 ⫾ 0.146ab
0.187 ⫾ 0.055abc
0.274 ⫾ 0.104ab
0.292 ⫾ 0.207ab
0.239 ⫾ 0.086abc
0.313 ⫾ 0.213a
0.245 ⫾ 0.086abc
0.177 ⫾ 0.091abc

1.64 ⫾ 0.33abc
1.55 ⫾ 0.51abc
1.67 ⫾ 0.53ab
1.74 ⫾ 0.33a
0.95 ⫾ 0.33d
1.22 ⫾ 0.48abcd
0.93 ⫾ 0.50d
1.09 ⫾ 0.34cd
0.73 ⫾ 0.22d
1.18 ⫾ 0.37bcd
0.73 ⫾ 0.27d

1 Values are means ⫾ SD, n ⫽ 6. Values within a column with the same superscripts are not different, P ⱖ 0.05.
2 Gerbils on baseline fed vitamin A-containing diet; gerbils on depletion fed vitamin A-deficient diet; gerbils on repletion fed either BC,

␤-carotene-containing diet; CC, carrot chip-containing diet; or ⫹VA, vitamin A-containing diet. These three diets had vitamin A activity ⬃6 ␮g RE/g
diet. The ⫺VA groups continued on depleted diet for an additional 2 and 4 wk period.

rats were fed commercial rat pellets containing 2600 ␮g
RAE/kg diet, and the rats were supplemented with either
retinol concentrate (30 – 45 ␮g RAE in 0.2 mL corn oil),
␤-carotene concentrate (30 – 45 ␮g RAE in 0.2 mL corn oil,
freeze-dried carrots (30 ␮g RAE), freeze-dried swamp cabbage
(30 ␮g RAE), or control (0.2 mL corn oil). As in the study by
Lee et al. (15), ␤-carotene was not detected in the serum of
rats in all groups (22). Perhaps the carotenes were cleared from
the plasma or converted into vitamin A quickly as a response
to the body’s need for retinol.
In this study 9-cis ␤-carotene was detected in the livers
of gerbils in the BC and CC groups. It was expected that
9-cis ␤-carotene would be found in the livers of the CC
gerbils because the carrot chips contained a large amount of
9-cis ␤-carotene, but not in the livers of the BC group.
Because 9-cis ␤-carotene was observed in the livers of gerbils fed the CC diet, this indicates that this isomer was
absorbed and biologically available. Levin and Mokady (29)
reported that 9-cis ␤-carotene was preferentially accumulated
and acted as a precursor of retinol in chicks. This may be why
the CC groups tended to have greater (P ⫽ 0.3065) liver
retinol stores than the BC groups. In the diet formulation and
data calculations, the 9-cis ␤-carotene was not included in the
calculation of vitamin A activity. Sweeney and Marsh (30)
reported that cis-isomers of provitamin-A carotenoids, such as
␣-carotene, ␤-carotene, and ␤-cryptoxanthin, have provitamin-A activities that are ⬃50% or less of that of corresponding all-trans carotenoids.
The presence of 9-cis ␤-carotene in the livers of gerbils in
the BC group as well as in the CC group may be due to
isomerization of the all-trans isomer to 9-cis before or during
absorption, or within tissues as hypothesized by Erdman et al.
(31) in a ferret study. Deming et al. (32) also observed the
isomerization of ␤-carotene in tissues of gerbils after a dose of
the all-trans and 9-cis ␤-carotene. In contrast to what happened in gerbils and ferrets, there may be an isomerization
from cis to trans isomers in humans. In a study by Johnson et
al. (33), 15 men were given oral doses of 9-cis ␤-carotene and
the serum concentrations of 9-cis ␤-carotene did not increase,
perhaps indicating poor absorption, isomerization from the cisto trans- form, or a very rapid tissue uptake. You et al. (34)

Downloaded from jn.nutrition.org by on June 23, 2007

␤-carotene. The Institute of Medicine (1) indicated that only
when liver vitamin A reserves fall below a critical concentration, thought to be ⬃20 ␮g/g liver (0.070 ␮mol/g), will plasma
retinol levels decrease. Because the liver stores of retinol of all
gerbils in the current study were ⬎58 ␮g/g liver (0.203 ␮mol/
g), the plasma retinol concentration was unchanged. Because
of the relatively insensitive relationship between plasma retinol concentration and liver vitamin A in the adequate range
of intake and because of the potential for confounding factors
to influence the levels and interpretation of plasma retinol
concentrations, plasma retinol concentration was not chosen
as a primary status indicator for human populations for estimating an average requirement for vitamin A (1).
Van het Hof et al. (26) reported that the bioavailability of
␤-carotene from vegetables in particular has been shown to be
low (14% from mixed vegetables) compared with that of
purified ␤-carotene added to a sample matrix. Rock et al. (27)
reported that bioavailability of ␤-carotene in processed carrots
was higher than in raw carrots. By measuring serum response of
healthy men to a single ingestion, Huang et al. (28) found that
the bioavailability of stir-fried carrots was 33% that of ␤-carotene beadlets. In this study, the liver vitamin A stores of the
CC group after 4 wk of repletion was not significantly different
from the BC group. This finding indicated that the provitamin-A carotenoids in the carrot chips were highly bioavailable. Deep-frying may also increase their bioavailability. In the
current study, the CC diet successfully reversed the marginal
vitamin A deficiency in gerbils similarly to those fed the BC
diet. The consumption of deep-fried carrot chips potentially
can reverse marginal vitamin deficiency in humans.
In this study, we did not detect any ␣-carotene, ␤-carotene,
or 9-cis ␤-carotene in the plasma of gerbils fed with BC and
CC diets. Perhaps the amounts of these carotenes available in
BC and CC diets were too low and all were transferred to the
liver or converted into retinoids. Using the same amount of
␤-carotene (3 ␮g RAE/g diet or 67.1 nmol/g diet) as used in
this study, Lee et al. (15) likewise did not detect ␤-carotene in
the plasma of gerbils. Only when these researchers used a
doubled amount of ␤-carotene (145.9 nmol/g diet) did they
detect the ␤-carotene in the plasma of gerbils fed the BC diet.
A feeding trial was performed by Tee et al. (22) on rats. The

SULAEMAN ET AL.

216

ACKNOWLEDGMENTS
We thank Edgar T. Clemens, Timothy P. Carr, and Randy L.
Wehling (University of Nebraska, Lincoln) for their beneficial suggestions throughout this study.

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623– 629.
9. Sulaeman, A., Giraud, D. W., Keeler, L., Taylor, S. L. & Driskell, J. A.
(2001) Changes in carotenoid, physicochemical, and sensory values of deepfried carrot chips during storage, p. 251 (abs.). Institute of Food Technologists’
Annual Meeting Book of Abstracts, Chicago, IL.
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11. Sulaeman, A., Keeler, L., Taylor, S. L., Giraud, D. W. & Driskell, J. A.
(2001) Carotenoid content, physicochemical, and sensory quality of deep-fried
carrot chips as affected by dehydration/rehydration, antioxidant, and fermentation. J. Agric. Food Chem. 49: 3253–3261.
12. Lederman, J. D., Overton, K. M., Hofmann, N. E., Moore, B. J., Thornton,
J. & Erdman, J. W., Jr. (1998) Ferret (Mustela putoius furo) inefficiently convert
␤-carotene to vitamin A. J. Nutr. 128: 271–279.
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Mongolian gerbils (Meriones unguiculatus) absorb ␤-carotene intact from a test
meal. J. Nutr. 124: 869 – 873.
15. Lee, C. M., Lederman, J. D., Hofmann, N. E. & Erdman, J. W., Jr.
(1998) The Mongolian gerbil (Meriones unguiculatus) is an appropriate animal
model for evaluation of the conversion of ␤-carotene to vitamin A. J. Nutr. 128:
280 –286.
16. Thatcher, A. J., Lee, C. M. & Erdman, J. W., Jr. (1998) Tissue stores of
␤-carotene are not conserved for later use as a source of vitamin A during
compromised vitamin A status in Mongolian gerbils (Meriones unguiculatus). J.
Nutr. 128: 1179 –1185.
17. National Research Council (1995) Nutrient Requirements of Laboratory Animals, 4th revised edition. National Academy Press, Washington, DC.
18. Barua, A. B. & Olson, J. A. (1998) Reversed-phase gradient highperformance liquid chromatographic procedure for simultaneous analysis of very
polar to nonpolar retinoids, carotenoids and tocopherols in animal and plant
samples. J. Chromatogr. Biol. Appl. 707: 69 –79.
19. Nierenberg, D. W. & Nann, S. L. (1992) A method for determining
concentrations of retinol, tocopherol, and five carotenoids in human plasma and
tissue samples. Am. J. Clin. Nutr. 56: 417– 426.
20. Sun, J., Giraud, D. W., Moxley, R. A. & Driskell, J. A. (1997) ␤-carotene
and ␣-tocopherol inhibit the development of atherosclerotic lesions in hypercholesterolemic rabbits. Int. J. Vitam. Nutr. Res. 67: 197–205.
21. Carr, T. P., Andersen, C. J. & Rudel, L. L. (1993) Enzymatic determination of triglyceride, free cholesterol, and total cholesterol in tissue lipid extracts.
Clin. Biochem. 26: 39 – 42.
22. Tee, E.-S., Lim, C.-L., Chong, Y.-H. & Khor, S.-C. (1996) A study of the
biological utilization of carotenoids of carrot and swamp cabbage in rats. Food
Chem. 56: 21–32.
23. Furusho, T., Kataoka, E., Yasuhara, T., Wada, M. & Masushige, S.
(2000) Retinol equivalence of carotenoids can be evaluated by hepatic vitamin
A content. Int. J. Vitam. Nutr. Res. 70: 43– 47.
24. Parvin, S. G., Bhaskaram, P. & Sivakumar, B. (2000) A novel pharmacokinetic approach to determine the relative efficiency of conversion of ␤-carotene to vitamin A in rats and children. Nutr. Res. 20: 633– 645.
25. Olson, J. A. (1987) Recommended dietary intakes (RDI) of vitamin A in
humans. Am. J. Clin. Nutr. 45: 704 –716.
26. Van het Hof, K. H., West, C. E., Weststrate, J. A. & Hautvast, J.G.A.J.
(2000) Dietary factors that affect the bioavailability of carotenoids. J. Nutr. 130:
503–506.
27. Rock, C. L., Lovalvo, J. L., Emenhiser, C., Ruffin, M. T., Flatt, S. W. &
Schwartz, S. J. (1998) Bioavailability of ␤-carotene is lower in raw than in
processed carrots and spinach in women. J. Nutr. 128: 913–916.

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demonstrated cis-trans isomerization during absorption in humans and reported that a large proportion of the 9-cis ␤-carotene dose was isomerized to trans ␤-carotene before entering
the bloodstream and increased the vitamin A value of 9-cis
␤-carotene. Furthermore, Rock et al. (27) found that the daily
consumption of processed carrots and spinach over a 4-wk
period produced a plasma ␤-carotene response that averaged
three times that associated with the consumption of the same
amount of ␤-carotene from these vegetables in the raw form (P
⫽ 0.09), despite the greater proportion of 9-cis ␤-carotene
isomers provided by the processed forms. These results suggested that the isomerization of ␤-carotene produced by heat
treatment did not negate the enhanced ␤-carotene uptake
associated with consuming cooked and pureed vegetables vs.
raw vegetables. Providing cooked and pureed vegetables rather
than raw vegetables would seem to be a better approach to
providing bioavailable ␤-carotene from carotenoid-rich foods,
which may have applicability for populations who rely on
these foods to meet vitamin A requirements.
Carotenoids are believed to have a variety of different
actions that are related to decreased risk of some degenerative
diseases (35). Therefore, the effects of having the carrot chip
product as a component of the diet of gerbils on their plasma
levels of triglycerides and cholesterol (LDL ⫹ VLDL, HDL,
and total) were also evaluated in this study. However, because
the amount of carrot chips, vitamin A, or ␤-carotene added in
the diets in this study was likely just enough to satisfy the
vitamin A requirement, no significant correlations between
the consumption of these diets and the plasma lipids were
observed. This is supported by the fact that no carotenes
(␣-carotene, ␤-carotene, or 9-cis ␤-carotene) were detected in
the gerbil plasma in this study. Chi et al. (36) investigated the
effects of dietary fats and antioxidants on blood pressure and
plasma lipids in spontaneously hypertensive rats. They found
that dietary antioxidants, consisting of tocopherol, ascorbic
acid, and ␤-carotene, did not affect plasma lipid levels. Only
the type of oil used in the diet influenced the blood pressure
and plasma lipids of these rats. Sun et al. (20) and Sulli et al.
(37), however, found that supplementation with a combination of ␣-tocopherol (0.5074 g/100 g dl-␣-tocopherol) and
␤-carotene (25 mg/kg body administered intravenously twice
weekly) significantly decreased plasma total and LDL cholesterol concentrations in hypercholesterolemic rabbits. However, this could be expected because the ␤-carotene intakes of
the rabbits in that experiment were higher on a body weight
basis than in the current study.
In conclusion, the provitamin-A carotenoids contained
in deep-fried carrot chips were biologically available to the
gerbils. After 4 wk, the gerbils marginally deficient in
vitamin A were repleted with the provitamin-A carotenoids
in the carrot chip diet. Therefore, deep-fried carrot chips
potentially may reverse marginal vitamin A deficiency in
humans.

CAROTENOIDS IN CARROT CHIPS AS PROVITAMIN-A
28. Huang, C.-J., Tang, Y.-L., Chen, C.-Y., Chen, M.-L., Chu, C.-C. & Hseu,
C.-T. (2000) The bioavailability of ␤-carotene in stir- or deep-fried vegetables
in men determined by measuring the serum response to a single ingestion. J.
Nutr. 130: 534 –540.
29. Levin, G. & Mokady, S. (1994) 9-cis ␤-carotene as a precursor of retinol
isomers in chicks. Int. J. Vitam. Nutr. Res. 64: 165–169.
30. Sweeney, J. P. & Marsh, A. C. (1971) Effect of processing on provitamin-A in vegetables. J. Am. Diet. Assoc. 59: 238 –243.
31. Erdman, J. W., Jr, Thatcher, A. J., Hofmann, N. E., Lederman, J. D.,
Block, S. S., Lee, C. M. & Mokady, S. (1998) All-trans ␤-carotene is absorbed
preferentially to 9-cis ␤-carotene, but the latter accumulates in the tissues of
domestic ferrets (Mustella putorius puro). J. Nutr. 128: 2009 –2013.
32. Deming, D. M., Teixeira, S. R. & Erdman, J. W., Jr. (2001) Isomerization of ␤-carotene in tissues from gerbils occurs following a dose of the all-trans
and 9-cis isomer. FASEB J. 15: A296 (abs.).

217

33. Johnson, E. J., Krinsky, N. I. & Russell, R. M. (1996) Serum response of
all-trans and 9-cis isomers of ␤-carotene in humans. J. Am. Coll. Nutr. 15: 620– 624.
34. You, C. S., Parker, R. S., Goodman, K. J., Swanson, J. E. & Corso, T. N.
(1996) Evidence of cis-trans isomerization of 9-cis-␤-carotene during absorption in humans. Am. J. Clin. Nutr. 64: 177–183.
35. Institute of Medicine, National Academy Sciences. (2000) Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids, p. 325.
National Academy Press, Washington, DC.
36. Chi, M. S., Galbreath, K. & Schimitz, D. (2001) Effect of dietary fats and
antioxidants on blood pressure and plasma lipids in spontaneously hypertensive
rats. FASEB J. 15: A261 (abs.).
37. Sulli, K. C., Sun, J., Giraud, D. W., Moxley, R. A. & Driskell, J. A.
(1998) Effects of ␤-carotene and ␣-tocopherol on the levels of tissue cholesterol and triglyceride in hypercholesterolemic rabbits. J. Nutr. Biochem. 9:
344 –350.

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Nutrient Metabolism

Mongolian Gerbils Can Utilize Provitamin-A Carotenoids
in Deep-Fried Carrot Chips1
Ahmad Sulaeman,2 David W. Giraud, M. Michelle Naslund and Judy A. Driskell3
Department of Nutritional Science and Dietetics, University of Nebraska, Lincoln, NE 68583-0806

KEY WORDS:

●

carrot chips

●

carotenoids

●

vitamin A

Vitamin A is important for vision, gene expression, reproduction, embryonic development, growth, and immune function (1). Humans need ⬍1 mg of vitamin A daily to maintain
health, yet it was estimated that 3 to 10 million children,
mostly in developing countries, become xerophthalmic and
250,000 to 500,000 go blind annually (2). An additional 250
million children under 5 y of age were estimated to be subclinically vitamin A-deficient and at risk of severe morbidity
and premature death (3).
Due to the enormous cost of vitamin A deficiency to
society, vitamin A intervention is of importance. Vitamin A
intervention approaches are commonly grouped into two main
control strategies: direct increase in vitamin A intake through
dietary modification with natural or fortified foods and supplements and indirect public health measures to control disease
frequency (4). For improving vitamin A status, food-based
approaches could be most effective where there is widespread
availability, variability, adequacy, and acceptability of vitamin
A-containing foods among targeted populations (3). In addition, food-based approaches deserve attention because they are

●

gerbil

more likely to be sustainable in the long term and will increase
the intake of other nutrients simultaneously (5). Such foods
are vegetables and fruits that have high provitamin-A carotenoid concentrations, especially ␤-carotene.
Deep-fried carrot chips that are high in provitamin-A carotenoids were developed in our laboratory as an alternative
product for intervention programs to overcome vitamin A
deficiency (6). Carrot chips contain fat, which is important
and a key factor in carotene absorption (7,8). Underwood (4)
reported that vegetable food-based interventions in vitamin
A-deficient areas can successfully improve vitamin A status,
particularly when dietary fat levels are also increased sufficiently. Carrot chips have a pleasant taste and an appealing
appearance; laboratory sensory evaluation and consumer studies indicated that this product was acceptable to both American and Southeast Asian consumers (unpublished data). The
retention of provitamin-A carotenoids during storage was
above 80%, which is important for optimal usage of this
product (9).
Using the conversion factors given by the National Research Council in 1989 (10), the deep-fried carrot chips developed in our laboratory had vitamin A activities of 7322–
8532 ␮g retinol equivalents (RE)4/100 g chips (11). Using the
new conversion factors (1), this product had vitamin A activities of 3661– 4266 ␮g retinol activity equivalents (RAE) per
100 g chips, an amount high enough to satisfy the human adult
daily need for vitamin A. However, to accurately measure the
biological activity of provitamin-A carotenoids in the carrot

1
Supported in part by the Nebraska Agricultural Research Division and
Research Report 13484.
2
Current address: Department of Community Nutrition and Family Resources, Bogor Agricultural University, IPB Darmaga Campus, Bogor 16680,
Indonesia.
3
To whom correspondence should be addressed. E-mail: jdriskell@unl.edu
4
Abbreviations used: BC, ␤-carotene-containing diet; CC, carrot chip-containing diet; RAE, retinol activity equivalents; RE, retinol equivalents; ⫹VA, vitamin
A-containing diet; ⫺VA, diet containing no vitamin A/provitamin-A carotenes.

0022-3166/02 $3.00 © 2002 American Society for Nutritional Sciences.
Manuscript received 5 September 2001. Initial review completed 16 October 2001. Revision accepted 15 November 2001.
211

Downloaded from jn.nutrition.org by on June 23, 2007

ABSTRACT Deep-fried carrot chips, containing provitamin-A carotenes, were developed as an alternative mode
of dietary intervention to combat vitamin A deficiency. The biological use of carotenoids in this product as vitamin
A precursors was evaluated in Mongolian gerbils. Male 4-wk-old gerbils were fed a diet containing all essential
nutrients for 1 wk. Then six gerbils were killed, and the remaining gerbils were fed the diet without vitamin A for 6
wk to produce marginal vitamin A deficiency. After depletion, six gerbils were killed and the remainder divided into
four groups of 12 gerbils each and fed vitamin A-containing diet (⫹VA), ␤-carotene-containing diet (BC), carrot
chip-containing diet (CC), or diet containing no vitamin A/provitamin-A carotenes (⫺VA). The first three diets
contained ⬃6 ␮g RE/g. Six gerbils from each group were killed after 2 wk of consuming these diets, and 6 after
4 wk. Final body weight and weekly food consumption did not differ among groups after 2 or 4 wk of repletion. Total
liver vitamin A stores of BC and CC gerbils killed after 4 wk of repletion were not different from those of gerbils killed
before depletion, but those of ⫺VA gerbils were significantly lower (P ⬍ 0.05) and those of ⫹VA gerbils were
significantly higher (P ⬍ 0.05). Plasma retinol levels of gerbils killed after 4 wk of repletion, including the ⫺VA group,
did not differ. Total liver ␣- and ␤-carotenes and 9-cis ␤-carotene contents of the CC group were significantly
higher (P ⬍ 0.05) than in the BC group after 4 wk of repletion. This carrot chip product effectively reversed vitamin
A deficiency in gerbils. J. Nutr. 132: 211–217, 2002.